I think he's saying that inside of the loop in FizzBuzz, it should look like something like this (Python-esque pseudocode, assuming for a second print() doesn't add a newline automatically):

    if x % 3 == 0:
        print("Fizz")

    if x % 5 == 0:
        print("Buzz")

    if x % 3 != 0 and x % 5 != 0:
        print(x)

    print("\n")

i.e. no special "FizzBuzz" case for when it's divisible by 15, it just naturally falls out of the first two if's. It's a bit of a silly objection though, the it's fine to write it as the author did.